CHAPTER XXI 



OHIO FIELD EXPERIMENTS 



ASIDE from the experiments outlined in Table 40, which deal 

 especially with manure, alone and reenforced with different mate- 

 rials, the Ohio Experiment Station has conducted, for 15 years, 

 two very extensive and valuable investigations by means of plot 

 experiments, relating to the maintenance of soil fertility. In 

 one of these a five-year rotation is .practiced on five separate 

 fields or series, each of which contains 30 tenth-acre plots about i 

 by 16 rods, each of the five crops, corn, oats, wheat, clover, and 

 timothy, being represented every year (excepting the clover and 

 timothy for the first two years). In the other investigation, 

 potatoes, wheat, and clover are grown in a three-year rotation on 

 three separate series, each of which contains 34 tenth-acre plots of 

 the same shape. Each of the crops is represented every year (ex- 

 cept wheat the first year and clover the first two years). The detail 

 plan of these experiments and the average results secured for the 

 15 years (1894 to 1908) are shown in Tables 82 and 83. 



Seasonal variations are too great to justify an attempt to de- 

 termine from the data secured in fifteen years (only 13 years with 

 clover and timothy) whether the productive power of the soil is 

 increasing or decreasing. It will be recalled that Jethro Tull grew 

 13 crops of wheat in succession on the same land without the use 

 of manure or fertilizers, and from the data secured the conclusion 

 was drawn, " that a good crop of wheat, for any number of years, 

 may be grown every year upon the same land without any manure 

 from first to last." A more recent similar illustration is furnished 

 by the Minnesota Experiment Station, showing average yields of 

 14.7 bushels of wheat from 1893 to 1898, and 17.2 bushels from 

 1899 to 1904, where wheat was grown every year without manure 

 or fertilizer. 



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